org.scijava.script.DefaultScriptInterpreter Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of scijava-common Show documentation
Show all versions of scijava-common Show documentation
SciJava Common is a shared library for SciJava software. It provides a plugin framework, with an extensible mechanism for service discovery, backed by its own annotation processor, so that plugins can be loaded dynamically. It is used by downstream projects in the SciJava ecosystem, such as ImageJ and SCIFIO.
/*
* #%L
* SciJava Common shared library for SciJava software.
* %%
* Copyright (C) 2009 - 2017 Board of Regents of the University of
* Wisconsin-Madison, Broad Institute of MIT and Harvard, and Max Planck
* Institute of Molecular Cell Biology and Genetics.
* %%
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
* #L%
*/
package org.scijava.script;
import java.lang.reflect.Method;
import javax.script.Bindings;
import javax.script.Compilable;
import javax.script.CompiledScript;
import javax.script.ScriptContext;
import javax.script.ScriptEngine;
import javax.script.ScriptException;
import org.scijava.log.LogService;
import org.scijava.plugin.Parameter;
import org.scijava.prefs.PrefService;
import org.scijava.util.LastRecentlyUsed;
/**
* The default implementation of a {@link ScriptInterpreter}.
*
* Credit to Jason Sachs for the multi-line evaluation (see
* his post on StackOverflow).
*
*
* @author Johannes Schindelin
* @author Curtis Rueden
*/
public class DefaultScriptInterpreter implements ScriptInterpreter {
private final ScriptLanguage language;
private final ScriptEngine engine;
private final History history;
@Parameter(required = false)
private PrefService prefs;
@Parameter(required = false)
private LogService log;
private final StringBuilder buffer;
private int pendingLineCount;
private boolean expectingMoreInput;
/**
* @deprecated Use {@link #DefaultScriptInterpreter(ScriptLanguage)} instead.
*/
@Deprecated
@SuppressWarnings("unused")
public DefaultScriptInterpreter(final PrefService prefs,
final ScriptService scriptService, final ScriptLanguage language)
{
this(language);
}
/**
* Creates a new script interpreter for the given script language.
*
* @param language {@link ScriptLanguage} of the interpreter
*/
public DefaultScriptInterpreter(final ScriptLanguage language) {
this(language, null);
}
/**
* Creates a new script interpreter for the given script language, using the
* specified script engine.
*
* @param language {@link ScriptLanguage} of the interpreter
* @param engine {@link ScriptEngine} to use, or null for the specified
* language's default engine
*/
public DefaultScriptInterpreter(final ScriptLanguage language,
final ScriptEngine engine)
{
language.getContext().inject(this);
this.language = language;
this.engine = engine == null ? language.getScriptEngine() : engine;
history = prefs == null ? null :
new History(prefs, this.engine.getClass().getName());
readHistory();
buffer = new StringBuilder();
reset();
}
// -- ScriptInterpreter methods --
@Override
public synchronized void readHistory() {
if (history == null) return;
history.read();
}
@Override
public synchronized void writeHistory() {
if (history == null) return;
history.write();
}
@Override
public synchronized String walkHistory(final String currentCommand,
final boolean forward)
{
if (history == null) return currentCommand;
history.replace(currentCommand);
return forward ? history.next() : history.previous();
}
@Override
public Object eval(final String command) throws ScriptException {
addToHistory(command);
return engine.eval(command);
}
/**
* {@inheritDoc}
*
* This implementation from Jason Sachs uses the following strategy:
*
*
* - Keep a pending list of input lines not yet evaluated.
* - Try compiling (but not evaluating) the pending input lines.
*
* - If the compilation is OK, we may be able to execute pending input
* lines.
* - If the compilation throws an exception, and there is an indication of
* the position (line + column number) of the error, and this matches the end
* of the pending input, then that's a clue that we're expecting more input,
* so swallow the exception and wait for the next line.
* - Otherwise, we either don't know where the error is, or it happened
* prior to the end of the pending input, so rethrow the exception.
*
*
* - If we are not expecting any more input lines, and we only have one line
* of pending input, then evaluate it and restart.
* - If we are not expecting any more input lines, and the last one is a
* blank one, and we have more than one line of pending input, then evaluate
* it and restart. Python's interactive shell seems to do this.
* - Otherwise, keep reading input lines.
*
*
* This helps avoid certain problems:
*
*
* - users getting annoyed having to enter extra blank lines after
* single-line inputs
* - users entering a long multi-line statement and only find out after the
* fact that there was a syntax error in the 2nd line.
*
*
* For further details, see SO
* #5584674.
*
*/
@Override
public Object interpret(final String line) throws ScriptException {
if (line.isEmpty()) {
if (!shouldEvaluatePendingInput(true)) return MORE_INPUT_PENDING;
}
if (pendingLineCount > 0) buffer.append("\n");
pendingLineCount++;
buffer.append(line);
final String command = buffer.toString();
if (!(engine instanceof Compilable)) {
// Not a compilable language.
// Evaluate directly, with no multi-line statements possible.
try {
return eval(command);
}
finally {
reset();
}
}
final CompiledScript cs = tryCompiling(command, //
getPendingLineCount(), line.length());
if (cs == null) {
// Command did not compile.
// Assume it is incomplete and wait for more input on the next line.
return MORE_INPUT_PENDING;
}
if (!shouldEvaluatePendingInput(line.isEmpty())) {
// We are still expecting more input.
return MORE_INPUT_PENDING;
}
// Command is complete; evaluate the compiled script.
try {
addToHistory(command);
return cs.eval();
}
finally {
reset();
}
}
@Override
public void reset() {
buffer.setLength(0);
pendingLineCount = 0;
expectingMoreInput = false;
}
@Override
public ScriptLanguage getLanguage() {
return language;
}
@Override
public ScriptEngine getEngine() {
return engine;
}
@Override
public Bindings getBindings() {
return engine.getBindings(ScriptContext.ENGINE_SCOPE);
}
@Override
public boolean isReady() {
return buffer.length() == 0;
}
@Override
public boolean isExpectingMoreInput() {
return expectingMoreInput;
}
// -- Helper methods --
private void addToHistory(final String command) {
if (history != null) history.add(command);
}
/**
* @return number of lines pending execution
*/
private int getPendingLineCount() {
return pendingLineCount;
}
/**
* @param lineIsEmpty whether the last line is empty
* @return whether we should evaluate the pending input. The default behavior
* is to evaluate if we only have one line of input, or if the user
* enters a blank line. This behavior should be overridden where
* appropriate.
*/
private boolean shouldEvaluatePendingInput(final boolean lineIsEmpty) {
if (isExpectingMoreInput()) return false;
return getPendingLineCount() == 1 || lineIsEmpty;
}
private CompiledScript tryCompiling(final String string, final int lineCount,
final int lastLineLength) throws ScriptException
{
CompiledScript result = null;
try {
final Compilable c = (Compilable) engine;
result = c.compile(string);
}
catch (final ScriptException se) {
boolean rethrow = true;
if (se.getCause() != null) {
final Integer col = columnNumber(se);
final Integer line = lineNumber(se);
// swallow the exception if it occurs at the last character
// of the input (we may need to wait for more lines)
if (isLastCharacter(col, line, lineCount, lastLineLength)) {
rethrow = false;
}
else if (log != null && log.isDebug()) {
final String msg = se.getCause().getMessage();
log.debug("L" + line + " C" + col + "(" + lineCount + "," +
lastLineLength + "): " + msg);
log.debug("in '" + string + "'");
}
}
if (rethrow) {
reset();
throw se;
}
}
expectingMoreInput = result == null;
return result;
}
private boolean isLastCharacter(final Integer col, final Integer line,
final int lineCount, final int lastLineLength)
{
if (col == null || line == null) return false;
final int colNo = col.intValue(), lineNo = line.intValue();
return lineNo == lineCount && colNo == lastLineLength ||
lineNo == lineCount + 1 && colNo == 0;
}
private Integer columnNumber(final ScriptException se) {
if (se.getColumnNumber() >= 0) return se.getColumnNumber();
return callMethod(se.getCause(), "columnNumber", Integer.class);
}
private Integer lineNumber(final ScriptException se) {
if (se.getLineNumber() >= 0) return se.getLineNumber();
return callMethod(se.getCause(), "lineNumber", Integer.class);
}
private static Method getMethod(final Object object,
final String methodName)
{
try {
return object.getClass().getMethod(methodName);
}
catch (final NoSuchMethodException e) {
// gulp
return null;
}
}
private static T callMethod(final Object object, final String methodName,
final Class cl)
{
try {
final Method m = getMethod(object, methodName);
if (m != null) {
final Object result = m.invoke(object);
return cl.cast(result);
}
}
catch (final Exception e) {
e.printStackTrace();
}
return null;
}
// -- Helper classes --
/** Container for a script language's interpreter history. */
private static class History {
@SuppressWarnings("unused")
protected static final long serialVersionUID = 2L;
private static final String PREFIX = "History.";
private final int MAX_ENTRIES = 1000;
private final PrefService prefs;
private final String name;
private final LastRecentlyUsed entries =
new LastRecentlyUsed<>(MAX_ENTRIES);
private String currentCommand = "";
private int position = -1;
/**
* Constructs a history object for a given scripting language.
*
* @param name the name of the scripting language
*/
public History(final PrefService prefs, final String name) {
this.prefs = prefs;
this.name = name;
}
/**
* Read back a persisted history.
*/
public void read() {
entries.clear();
for (final String item : prefs.getIterable(getClass(), PREFIX + name)) {
entries.addToEnd(item);
}
}
/**
* Persist the history.
*
* @see PrefService
*/
public void write() {
prefs.putIterable(getClass(), entries, PREFIX + name);
}
/**
* Adds the most recently issued command.
*
* @param command the most recent command to add to the history
*/
public void add(final String command) {
entries.add(command);
position = -1;
currentCommand = "";
}
public boolean replace(final String command) {
if (position < 0) {
currentCommand = command;
return false;
}
return entries.replace(position, command);
}
/**
* Navigates to the next (more recent) command.
*
* This method wraps around, i.e. it returns {@code null} when there is no
* more-recent command in the history.
*
*
* @return the next command
*/
public String next() {
position = entries.next(position);
return position < 0 ? currentCommand : entries.get(position);
}
/**
* Navigates to the previous (i.e less recent) command.
*
* This method wraps around, i.e. it returns {@code null} when there is no
* less-recent command in the history.
*
*
* @return the previous command
*/
public String previous() {
position = entries.previous(position);
return position < 0 ? currentCommand : entries.get(position);
}
@Override
public String toString() {
final StringBuilder builder = new StringBuilder();
int pos = -1;
for (;;) {
pos = entries.previous(pos);
if (pos < 0) break;
if (builder.length() > 0) builder.append(" -> ");
if (this.position == pos) builder.append("[");
builder.append(entries.get(pos));
if (this.position == pos) builder.append("]");
}
return builder.toString();
}
}
}